Dissertation/Thesis Abstract

Measurements of the top quark pair production cross section and branching ratio to a W-boson and bottom quark using the semi-leptonic and dilepton final states with the ATLAS detector at the LHC
by Calkins, Robert E., Ph.D., Northern Illinois University, 2012, 241; 3552277
Abstract (Summary)

In the Standard Model, the top quark plays a unique role as the heaviest known fundamental particle and as a quark that decays before it is able to hadronize. Top quarks are expected to decay to a W-boson and a b-quark nearly 100% of the time. If the branching ratio of tWb is lower than one, the distribution of the number of b-tagged jets will shift to lower multiplicities. A simultaneous likelihood fit to the number of b-tagged jets distributions in the lepton+jets and dilepton channels is performed on 4.7 fb−1 of data collected by the ATLAS detector to extract both the branching ratio and the tt¯ cross section. The branching ratio of tWb, R, is measured to be 1.06±0.11, which is consistent with the Standard Model value. This is the first measurement of the t Wb branching ratio performed with the ATLAS detector using both the lepton+jets and dilepton channels at the LHC. The tt¯ cross section is measured to be [special characters omitted] pb, which agrees with NNLO predictions.

Indexing (document details)
Advisor: Chakraborty, Dhiman
Commitee: Arguin, Jean-Francois, Blazey, Gerald, Martin, Stephen
School: Northern Illinois University
Department: Physics
School Location: United States -- Illinois
Source: DAI-B 74/06(E), Dissertation Abstracts International
Subjects: Particle physics
Keywords: Branching ratio, Cross section, Dilepton final states, Large Hadron Collider, Pair production, Top quarks, W bosons
Publication Number: 3552277
ISBN: 9781267906960
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